title: ampC cephalosporinase of Escherichia coli K-12 has a different evolutionary origin from that of beta-lactamases of the penicillinase type.
abstract: A 1536-nucleotide-long sequence that carries the ampC beta-lactamase gene of the Escherichia coli K-12 chromosome has been determined. This gene codes for a protein of 377 amino acids, of which the first 19 amino acids form a signal peptide. The molecular weight of the mature enzyme was determined to be 39,600. The ampC beta-lactamase with a substrate specificity for cephalosporins showed no significant sequence homologies with beta-lactamases of the penicillinase type or with D-alanine carboxypeptidases. However, because the region around serine-80 of the ampC beta-lactamase has extensive homology with an active-site fragment of the Pseudomonas aeruginosa cephalosporinase, we suggest that the ampC cephalosporinase as well as related cephalosporinases form a distinct group of serine beta-lactamases that have an evolutionary origin different from that of the serine penicillinases and thus constitute a new class of beta-lactamases.
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D005075:Biological Evolution; D002510:Cephalosporinase / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005796:Genes; D005798:Genes, Bacterial; D005809:Genes, Regulator; D012694:Serine; D014158:Transcription, Genetic; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics*
chemical_list: D012694:Serine; D002510:Cephalosporinase; D001618:beta-Lactamases